PROJECT SUMMARY The execution of learned sequential motor behaviors, like those involved in playing a well learned tune on the piano, are thought to be supported by precise sequences of neuronal activity in the brain. However, probing the ties between sequential neuronal activity, neuronal connectivity and behavior is challenging without methods for simultaneously observing and controlling neuronal activity with spatial and temporal precision. We propose to apply all-optical physiological methods, combining concurrent optogenetic manipulation, and population calcium imaging, to map the functional organization of circuits involved in a well-studied sequential motor behavior. This research will involve dissemination of cutting-edge optical methods central to the BRAIN Initiative and facilitate a better understanding of how patterns of neuronal activity underlying precise complex behaviors are generated in the brain.